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International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064
Index Copernicus Value (2013): 6.14 | Impact Factor (2013): 4.438
Volume 4 Issue 5, May 2015
www.ijsr.net Licensed Under Creative Commons Attribution CC BY
Finite Element Analysis of Friction Welding
Process for UNS C23000 Brass and AISI 1021 Steel
A. Raviteja1, A. Chennakesava Reddy
2
1PG student, Department of Mechanical Engineering, JNTUH College of Engineering, Kukatpally, Hyderabad – 500 085, Telangana, India
2Professor, Department of Mechanical Engineering, JNTUH College of Engineering, Kukatpally, Hyderabad – 500 085, Telangana, India
Abstract: The purpose of this work was to weld dissimilar metals of UNS C23000 brass and AISI 1021 steel by continuous drive fric-
tion welding. The finite element analysis has been carried out to model the continuous drive friction welding. The process parameters
have been optimized using Taguchi techniques. The optimal process parameters for UNS C23000 brass and AISI 1021 steel are
found to be frictional pressure of 60 MPa, frictional time of 4 sec, rotational speed of 1500 rpm and forging pressure of
62.5 MPa.
Keywords: UNS C23000 brass, AISI 1021 steel, finite element analysis, Taguchi, continuous drive friction welding.
1. Introduction
Friction welding is a solid-state welding process that allows
material combinations to be joined than with any other weld-
ing process. In continuous drive friction welding, one of the
workpieces is attached to a motor driven unit while the other
is restrained from rotation as showed in figure 1a. The motor
driven workpiece is rotated at a predetermined constant
speed. The workpieces to be welded are forced together and
then a friction force is applied as shown in figure 1b. Heat is
generated because of friction between the welding surfaces.
This is continued for a predetermined time as showed in fig-
ure 1c. The rotating workpiece is halted by the application of
a braking force. The friction force is preserved or increased
for a predetermined time after the rotation is ceased (fig-
ure1d). Figure1also illustrates the variation of welding speed,
friction force and forging force with time during various
stages of the friction welding process.
Figure 1: Friction welding
Even metal combinations not normally considered compati-
ble can be joined by friction welding, such as aluminum to
steel, copper to aluminum, titanium to copper and nickel
alloys to steel. As a rule, all metallic engineering materials
which are forgeable can be friction welded, including auto-
motive valve alloys, maraging steel, tool steel, alloy steels
and tantalum [1, 2]. With friction welding, joints are possible
between not only two solid materials or two hollow parts, but
also solid material/hollow part combinations can be reliably
welded. However, the shape of a fusion zone in friction
welding is dependent the force applied and the rotational
speed. If the applied force is too high or the rotational speed
is too low, the fusion zone at the centre of the joint will be
narrow as showed in figure 2a. On the other hand, if the ap-
plied force is too low or the rotational speed is too high, the
fusion zone at the centre of the joint will be wider as showed
in figure 2b. In both the cases, the result is poor weld joint
strength.
Figure 2: Effect of force and rotational speed in friction
welding
In the friction welding process, the developed heat at the
interface raises the temperature of workpieces rapidly to val-
ues approaching the melting range of the material. Welding
occurs under the influence of pressure that is applied when
heated zone is in the plastic range, as mentioned [3]. The
foremost difference between the welding of similar materials
and that of dissimilar materials is that the axial movement is
unequal in the latter case whilst the similar materials expe-
rience equal movement along the common axis. This prob-
lem arises not only from the different coefficients of thermal
expansion, but also from the distinct hardness values of the
dissimilar materials to be joined. Joint and edge preparation
is very important to produce distortion free welds. The solid-
state diffusion is slow in the wider joints [4].The intermetal-
lic compounds can change the micro hardness near the joint
interface of dissimilar metals [5].
Low carbon steel and copper alloys are widely applied pros-
pects because of their economic value, plus good mechanical
Paper ID: SUB154501 1691
International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064
Index Copernicus Value (2013): 6.14 | Impact Factor (2013): 4.438
Volume 4 Issue 5, May 2015
www.ijsr.net Licensed Under Creative Commons Attribution CC BY
and physical properties. It is an easy process to weld these
materials by themselves. Unfortunately, most engineering
materials have to join with dissimilar counterparts. Thus, it is
difficult to obtain good-quality weld joints using molten
welding methods. Some defects and intermetallic phases can
occur during the process because of the great differences
between Fe and Cu in physical, mechanical, and chemical
properties. Therefore, friction welding of these materials
needs to be eased by ensuring that both the workpieces de-
form similarly. In this context, this research work aims at
finite element analysis of friction welding process for UNS
C23000 brass and AISI 1021 steel.
2. Finite Element Modeling
In this study, ANSYS workbench (15.0) software was used
in the coupled deformation and heat flow analysis during
friction welding of UNS C23000 brass and AISI 1021 steel.
An axisymmetric 3D model [6] of AISI 1021 steel - UNS
C23000 brass rods of 25.4 mm diameter and 100 mm length
was made using ANSYS workbench as shown in figure 3.
Hexahedron elements [7] were used to mesh the AISI 1021
steel and UNS C23000 brass rods. The rotating part was
modeled with 3298 elements and 14904 nodes and the non-
rotating part was meshed with 16493 nodes and 3672 ele-
ments.
Figure 3: Finite element modeling of friction welding
Figure 4: The boundary conditions
The boundary conditions are mentioned in figure 4. First the
transient thermal analysis was carried out keeping AISI 1021
steel rod stationary and C23000 brass rod in rotation. The
coefficient of friction 0.2 was applied at the interface of UNS
C23000 brass and AISI 1021 steel rods. The convection heat
transfer coefficient was applied on the surface of two rods.
The heat flux calculations were imported from ANSYS
APDL commands and applied at the interface. The tempera-
ture distribution was evaluated. The thermal analysis was
coupled to static structural analysis. For the structural analy-
sis the rotating (C23000 brass) rod was brought to stationary
and the forging pressure was applied on the AISI 1021 steel
rod along the axis of rod. The AISI 1021 steel rod was al-
lowed to move in the axial direction. The structural analysis
was carried out for the equivalent stress and strain, total and
directional deformation. The contact analysis was also car-
ried out to estimate the depth of penetration and sliding of
the material at the interface.
Table 1: Process parameters and levels Factor Symbol Level–1 Level–2 Level–3 Frictional Pressure, MPa A 40 50 60 Frictional time, Sec B 4 5 6
Rotational speed C 1000 1250 1500 Forging pressure, MPa D 50.0 62.5 75.0
The analysis of friction welding was carried out as per the
design of experiments using Taguchi techniques. The process
parameters and their levels are given table-1. The orthogonal
array (OA), L9 was selected for the present work. The para-
meters were assigned to the various columns of O.A. The
assignment of parameters along with the OA matrix is given
in table 2.
Table 2: Orthogonal Array (L9) and control parameters Treat No. A B C D
1 1 1 1 1 2 1 2 2 2 3 1 3 3 3 4 2 1 2 3 5 2 2 3 1 6 2 3 1 2 7 3 1 3 2 8 3 2 1 3 9 3 3 2 1
3. Results and Discussion
The temperature distribution from the transient thermal anal-
ysis; equivalent stress and directional deformation from the
structural analysis; penetration and sliding from the contact
analysis are discussed in the following sections.
3.1 Influence of Parameters on Temperature Distribution
Table – 3 gives the ANOVA (analysis of variation) summary
of raw data. The Fisher’s test column establishes all the pa-
rameters (A, B, C and D) accepted at 90% confidence level.
The percent contribution indicates that the friction pressure,
A contributes 43.81% of variation, B (friction time) aids
9.3% of variation, and C (rotational speed) influences
45.62% of variation on the temperature distribution. The
effect of forging pressure is negligible.
Table 3: ANOVA summary of the temperature distribution
Source Sum 1 Sum 2 Sum 3 SS v V F P
A 4520 5684 6315 276354 2 138176.9 32209.07 43.81
B 5107 5468 5943 58679 2 29339.5 6839.044 9.3
C 4680 5327 6512 287771 2 143885.4 33539.72 45.62
D 5462 5678 5378 7984 4 1995.94 465.25 1.26
e 30 7 4.29 1 0.01
T 19769 22157 24149 630817 17 100
Note: SS is the sum of square, v is the degrees of freedom, V
is the variance, F is the Fisher’s ratio, P is the percentage of
contribution and T is the sum squares due to total variation.
The temperature developed in the welding rods is directly
proportional to the frictional pressure, frictional time and
rotational speed as shown in figure 5, 6 & 7. In fact this is
natural phenomena. Form figure 8 it is observed that the
temperature is very high at the interface. The trial 7 gives the
highest temperature generation and trial 1 gives the lowest
temperature generation in the rods. Change of temperature
field is generated by heat flux that depends on: frictional
Paper ID: SUB154501 1692
International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064
Index Copernicus Value (2013): 6.14 | Impact Factor (2013): 4.438
Volume 4 Issue 5, May 2015
www.ijsr.net Licensed Under Creative Commons Attribution CC BY
pressure on the contact surface, relative velocity of the two
faces, frictional time and coefficient of friction.
Figure 5: Influence of frictional pressure on temperature
Figure 6: Influence of frictional time on temperature
Figure 7: Influence of rotational speed on temperature
3.2 Influence of Parameters on Equivalent Stress
The ANOVA summary of the elastic modulus is given in
Table 4. The Fisher’s test column ascertains all the parame-
ters (A, B, C and D) accepted at 90% confidence level in-
fluencing the variation in the equivalent stress. The contribu-
tion of friction pressure, frictional time, rotational speed and
forging pressure are 48.22%, 3.7%, 44.93%, and 3.03% re-
spectively towards variation in the effective stress.
It is observed from table 5 that the equivalent stress is 440.61
MPa for trail 7 at the end of frictional heating and is 272.64
MPa at the end of forging pressure. It is also observed from
table 5 that the equivalent stress is 205.52 MPa for trail 1 at
the end of frictional heating and is 138.49 MPa at the end of
forging pressure. During friction heating stage any surface
irregularities are removed, the temperature increases in the
vicinity of the welded surfaces, and an interface of visco-
plastic aluminum is formed. During forging pressure stage
there is significant thermo-plastic deformation of aluminum
in the contact area. In result of this is formation of a flange-
like flash. The process of welding takes place due to the plas-
tic and diffusion effects.
Figure 8: Temperature distribution during different trials
Table 4: ANOVA summary of the equivalent stress
Source Sum 1 Sum 2 Sum 3 SS v V F P
A 1463.71 1864.46 2110.36 35512.66 2 17756.33 3272.48 48.22
B 1909.20 1799.76 1729.57 2731.71 2 1365.85 251.73 3.70
C 1545.23 1733.20 2160.10 33091.24 2 16545.62 3049.35 44.93
D 1758.88 1907.51 1772.14 2255.03 4 563.76 103.90 3.03
e 37.98 7 5.43 1.00 0.12
T 6677.02 7304.92 7772.17 73628.62 17 100
The equivalent stress increases with an increase in the fric-
tional pressure and, rotational speed as shown in figure 9 &
10.
Paper ID: SUB154501 1693
International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064
Index Copernicus Value (2013): 6.14 | Impact Factor (2013): 4.438
Volume 4 Issue 5, May 2015
www.ijsr.net Licensed Under Creative Commons Attribution CC BY
Figure 9: Influence of frictional pressure on equivalent
stress.
Figure 10: Influence of rotational speed on equivalent stress.
Table 5: Equivalent stress values under different trials
At end of frictional heating At end of forging
1
2
3
4
5
6
7
8
9
Table 6: ANOVA summary of the directional deformation
Source Sum 1 Sum 2 Sum 3 SS v V F P
A 1.449 1.932 2.031 0.03 2 0.015 34.88 28.84
B 1.484 1.764 2.164 0.04 2 0.02 46.50 38.19
C 1.493 1.761 2.157 0.04 2 0.02 46.50 38.19
D 1.837 1.834 1.741 0 4 0 0.00 1.61
e -0.003 7 -0.0004 1.00 -6.83
T 6.263 7.291 8.092 0.107 17 100
3.3 Influence of parameters on total deformation
The ANOVA summary of the directional deformation is giv-
en in Table 6. The Fisher’s test column ascertains all the pa-
rameters (A, B, C, D) accepted at 90% confidence level in-
fluencing the variation in the directional deformation. The
frictional pressure contributes 28.84%; frictional time and
rotational speed influences 38.19 % each towards variation
in the directional deformation. The influence of forging pres-
sure is negligible.
Figure 11: Influence of frictional pressure on deformation
Figure 12: Influence of frictional time on deformation
Paper ID: SUB154501 1694
International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064
Index Copernicus Value (2013): 6.14 | Impact Factor (2013): 4.438
Volume 4 Issue 5, May 2015
www.ijsr.net Licensed Under Creative Commons Attribution CC BY
Figure 13: Influence of rotational speed on deformation
The total deformation increases with an increase in the fric-
tional pressure, frictional time and rotational speed as shown
in figure 11, 12 & 13. In the first numerical iteration (ther-
mal) the external load generates uniform pressure on the con-
tact surface and consequently linearly changing heat flux.
There is a gap between AISI 1021 steel and UNS C23000
brass as seen from table 6. In the next iteration (static) the
forging pressure on the contact surface forces the material to
penetrate and slid. There is no gap between steel aluminum.
The extruded shape gradually forms near the welded joint
during the welding process. The extruded shape is asymme-
tric, as shown in table 6. It results from non-uniform material
properties along the radial direction of the specimen during
welding.
Table 6: Directional deformation values under different tri-
als
At end of frictional heating At end of forging
1
2
3
4
5
6
7
8
9
3.4 Influence of Parameters on Penetration and Sliding
In friction welding of UNS C23000 brass and AISI 1021
Steel, only UNS C23000 brass is consumed in the form of
flash due to softer and high thermal conductive material as
most of the heat generated at the interface is transferred to
UNS C23000 brass. The deformation of AISI 1021 Steel is
negligible due to its higher hardness value, and higher melt-
ing point as shown in table 7. In the case of trail 1 the inter-
face layer has not produced a good metallic bond between
AISI 1021 steel and UNS C23000 brass. In the case of trail 4
and 7 the interface layer has produced a good metallic bond
between aluminum and steel. The penetrations of trails 4 and
7 are 0.0017 and 0.002 mm respectively. A closer look at the
penetration and sliding images shows that the failure of good
bonding has taken place largely by interface separation. One
factor may be the uneven rate of heat generation. Due to this
uneven rate of heat input, the amount of melt-off for each
cycle for welding this combination of steel and UNS C23000
brass.
The optimal process parameters for UNS C23000 brass and
AISI 1021 Steel are found to be frictional pressure of 35
MPa, frictional time of 3 sec, rotational speed of 1500 rpm
and forging pressure of 37.5 MPa. For this dissimilar metals
of aluminium and steel, the forging pressure should be higher
than the frictional pressure. The experimental fricitional
welding validateds the the seventh trial conditions as shown
in figure 17.
Table 7: Sliding and penetration values under different trials
Sliding Penetration
1
2
3
4
5
6
Paper ID: SUB154501 1695
International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064
Index Copernicus Value (2013): 6.14 | Impact Factor (2013): 4.438
Volume 4 Issue 5, May 2015
www.ijsr.net Licensed Under Creative Commons Attribution CC BY
7
8
9
Figure 17: Welding UNS C23000 brass and AISI 1021 steel
with different frictional pressures
4. Conclusions
This study shows that the AISI 1021 steel and UNS C23000
brass is good if the operating conditions: frictional pressure
of 60 MPa, frictional time of 4 sec, rotational speed of 1500
rpm and forging pressure of 62.5 MPa. For friction welding
of UNS C23000 brass and AISI 1021 steel the forging pres-
sure should be higher than the frictional pressure. For this
condition of welding there was good penetration and sliding
of materials at the welding interface resulting a good me-
chanical bonding.
5. Acknowledgements
The author acknowledges with thanks University Grants
Commission (UGC) – New Delhi for sectioning R&D
project.
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Paper ID: SUB154501 1696